People holding mobile phones are silhouetted against a backdrop projected with the Twitter logo in this illustration picture taken in Warsaw September 27, 2013. Twitter Inc, the eight-year-old online messaging service, gave potential investors their first glance at its financials on Thursday when it publicly filed its IPO documents, setting the stage for one of the most-anticipated debuts in over a year. Picture taken September 27. REUTERS/Kacper Pempel (POLAND – Tags: BUSINESS TELECOMS LOGO)